Digital FIR Filter Correction for High-Speed Data Acquisition Frequency Response
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Solution Overview
Problem
High-speed data acquisition devices face accuracy issues due to hardware variances in electrical components, leading to inaccurate identification of power quality issues in power systems, primarily caused by parasitic and expected responses of elements in anti-aliasing filters.
Innovation Solution
The method involves sampling signals at a first rate, interpolating the digital data stream to increase the sample rate, applying finite impulse response (FIR) filters to correct for parasitic and anti-aliasing filter responses, and decimating the signal to reduce sampling rate and correct for gain errors, using a combination of anti-aliasing filters and CIC filters to improve frequency response accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If anti-aliasing filters are used in the measurement circuit, then signal accuracy is improved, but frequency response accuracy deteriorates due to parasitic and expected responses of filter elements
Solution Approach 1:
The patent converts the harmful parasitic responses of anti-aliasing filter elements into beneficial corrections by measuring and compensating for these effects. The system characterizes the parasitic responses and applies correction factors to compensate for the frequency response distortion, thereby converting the harmful effect into a beneficial correction mechanism.
Solution Approach 2:
The patent implements feedback by measuring the actual frequency response of the measurement circuit including parasitic effects, comparing it with the desired response, and applying correction through digital signal processing. The correction factors are determined based on the measured parasitic responses and applied to compensate for frequency response inaccuracies.
2Productivity
If hardware components are used in the data acquisition device, then signal processing capability is improved, but accuracy deteriorates due to hardware variances in electrical components
Solution Approach 1:
The patent changes parameters by using digital correction factors that are determined based on measured parasitic responses and hardware characteristics. Instead of relying solely on fixed hardware designs, the system adapts correction parameters to compensate for hardware variances, thereby maintaining accuracy despite component variations.
Solution Approach 2:
The patent creates a digital model or copy of the hardware response characteristics and uses this model to compensate for actual hardware variations. By measuring the parasitic responses and creating correction factors that replicate the desired compensation, the system achieves accuracy without requiring perfect hardware consistency.
3Speed
If sampling rate is increased to capture high-speed signals, then transient detection capability is improved, but data processing complexity increases
Solution Approach 1:
The patent extracts and removes the complexity of high-rate data processing by using decimation to reduce the sampling rate after correction. By separating the correction process from the high-speed capture process, the system maintains the ability to capture fast transients while reducing the complexity of subsequent data processing through rate reduction.
Data Source
AI summary
A method for improving frequency response of a high-speed data acquisition device includes sampling signals received at an input of the high-speed data acquisition device at a first sampling rate and generating a digital data stream representative of the sampled input signals. The digital data stream is interpolated to generate an interpolated digital signal with a higher sample rate than the first sampling rate, and one or more finite impulse response (FIR) filters are applied to the interpolated digital signal to generate a filtered digital signal. The filtered digital signal corrects for: parasitic and/or expected response of elements from the network of resistors and capacitors in the anti-aliasing filter in the high-speed data acquisition device, and select anti-aliasing filter response characteristics. The filtered digital signal is decimated to reduce the sampling rate of the filtered digital signal and generate a decimated digital signal.